﻿<%@ page pageEncoding="UTF-8"%>
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
Color getRandColor(int fc,int bc){//给定范围获得随机颜色
         Random random = new Random();
         if(fc>255) fc=255;
         if(bc>255) bc=255;
         int r=fc+random.nextInt(bc-fc);
         int g=fc+random.nextInt(bc-fc);
         int b=fc+random.nextInt(bc-fc);
         return new Color(255,255,255);
         }
%>
<%
//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

// 在内存中创建图象
int width=75, height=25;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
Graphics g = image.getGraphics();

//生成随机类
Random random = new Random();

// 设定背景色
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);

//设定字体
g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,22));




// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(getRandColor(160,200));
for (int i=0;i<10;i++)
{
         int x = random.nextInt(width);
         int y = random.nextInt(height);
         int xl = random.nextInt(12);
         int yl = random.nextInt(12);
         g.drawLine(x,y,x+xl,y+yl);
}

// 取随机产生的认证码(4位数字)
String sRand="";
for (int i=0;i<4;i++){
     String rand=String.valueOf(random.nextInt(10));
     sRand+=rand;
     // 将认证码显示到图象中
     g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
     g.drawString(rand,13*i+6,16);
}

// 将认证码存入SESSION
session.setAttribute("rand",sRand);

System.out.println("Rand in Image:::::" + session.getAttribute("rand"));


// 图象生效
g.dispose();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());

out.clear();
out = pageContext.pushBody();

//将认证码存入SESSION
session.setAttribute("rand",sRand);

%>
